Telephone-exchange system



Jan. 8 1924.

W. B. STRICKLER TELEPHONE EXCHANGE S\YSTEM Filed Oct. 15. 1920 3 Sheets-Sheet 1 /m en 70/1- h d/fer 5. jf'n'ck/er Jan. 8 1924.

- 1,480,229 W. B. STRICKLER TELEPHONE EXCHANGE SYSTEM Filed Oct. 15, 3 Sheets-Sheet 2 Jan, 1924.

3 Sheets-Sheet 5 Filed Oct. '15

Patented Jan. 8, 1924.

" nane tblllEQ S'l'aifig OFFICE.

WALTER B. .SIRIGKLER, OF EAST ORANGE, NE?! JERSEY, ASSIGNOR T0 WESTERN ELEC- TRIO COMPANY, INCORPORATED, G3? HEY V YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed. Qctober 15, 1920. Serial No. 417,209.

To all whom it may concern Be it known that I, VVALTER B. STRIOK- Len, a citizen of the United States, residing at East Orange, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone. exchange systems and particularly to cord and trunk circuit arrangements for use at a manual private branch exchange for the purpose of interconnecting subscribers lines terminating thereat with subscribers of a main automatic exchange.

It has been the usual practice in such systems to provide each operator of the private branch exchange with an impulse sender by means of which, on outgoing calls to the main automatic exchange, the setting of switches at said main exchange are con trolled. Various ways of associating the impulse sender with the cord circuit have been provided, one of which consisted of a key which upon actuation served to disconnect the answering end of the cord circuit from the calling end and to connect the impulse sender to the calling end. If the operator failed to restore the key after completion of the impulse sender operation, and the walled subscriber responded, it'was impossible for the calling and called subscribers to converse due to the answering and calling end of the cord circuit being severed.

t is the object of the present invention to obviate this diiiiculty by providing a key for each cord circuit which, upon actuation, serves to connect the operators telephone set tn the answering and calling ends of the cord circuit and to associate the impulse sender with the calling end of the cord circuit when the impulse sender is actuated. The operator, having ascertained the number of the station at the automatic exchange desired by the calling subscriber, inserts the calling end of the cord circuit into an idle trim. circuit extending from the private branch to the automatic exchange. The operator then 'actuates the impulse sender. Upon the initial actuation of the impulse sender, the talking conductors of the cord circuit are rendered discontinuous and the interrupting contacts of the impulse sender are connected to the calling end of the cord circuit. If the operator fails to restore the key, after'having completed the impulse sending'operation', a talking path for the calling and called subscribers independent oi the normal talking path of the cord circuit and common to the operators position is provided.

Another object of the invention is to provide in a repeating trunk circuit, means for preventing the false operation of switches, when a cord circuit is connected to the trunk circuit for the purpose of enabling the operator of the private branch exchange to control the setting of the switches at the automatic exchange.

To attain one of the objects of the invention an inductive path normally disconnected from the cord circuits of the position and common thereto is connected in operative relationship with the answering and calling ends or" a cord circuit after the listening key and impulse sender have been operated. normal removes the inductive path and the impulse sender from operative relationship with the cord circuit, whereupon they are available for use with another cord circuit.

To accomplish another object of the invention, a relay connected to one of the talking conductors of the inner section of the repeating trunk circuit, prevents the closure of a bridge across the outer section of the repcating trunk circuit until the plug of the corn circuit is fully inserted into the jack of the trunk circuit.

For a more complete understanding of this invention reference may be had to the following description in connection with the accompanying drawings in which Fig. 1 when placed to the left of Fig. 2 shows a system containing an embodiment of the invention. Fig. 3 shows a modified form of an embodiment of the invention relating to the cord circuit.

Referring to Fig. 1 of the drawings, there is shown a common battery station A, which may be of any well-known type, having associated therewith a line jack 3, a line relay 1, and a line signal 2. The operators cord circuit 0 is adapted for use for either connecting two manual lines terminating at the private exchange or for connecting a Restoring the listening key to.

manual line with the automatic exchange. This cord circuit comprises the usual answering and cal ing plugs l and 23, normally connected together through the repeating coil The cord circuit O is provided with sugerv sory relays 6 and 12, and supervisory lamps 7 and 27 connected in a manner wellknown in the art, for the purpose of proriding supervision in interconnecting lines terminating in the branch exchange. When the cord circuit is used for interconnecting a manual line with a subscriber in the automatic exhange, lamp 7 serves as a supervisory signal and lamp 27 as a recall signal. The corn; circuit O is provided with the usual ringing keys 10 and 1 1-. An answering key K is provided for the purpose of connecting the operators talking set (not shown) with the cord circuit O. This key when actuated performs the additional function of associating the impulse sender S with the cord circuit, when the cord circuit is utilized for interconnecting a line terminating at the branch exchange with the trunk circuit T (shown in Fig. 2) extending to the auto-.

matic exchange. The impulse sender S, the relays 15 and 18, resistance 19, coil 20 and condensers 16 and 17 are common to the operators position, whereas the relay 22, which serves to disconnect the answering from the calling end of the cord circuit 0 during the sending of impulses, is individual to each cord circuit ot the operatofls position. Relays 15 and 18 are energized each time the sender S is actuated and deenergized each time the sencer 51 returns to normal. Relay 22 which when operated serves to disconnect the answering from the calling end, is energized upon the initial actuation ot sender S, and remains energized until the listening key K is restored to normal. It the operator fails to restore the listening key as soon as the impulse sending operation is completed and the called subscriber re sponds, talking circuit is provided for the callin and called subscribers through the induct. re path includmg the condensers 16 and 17, said path being independent of the normal talking path and common to all the cord circuits of the position.

Referring to Fig. 2 of the drawings, there is shown a trunk circuit T which is of the two-way type and terminates at one end in a jack 24: at the ooerators position. Assoch ated with the jack of the trunk circuit is a bu v signal 56. The jack and signal may be multipled to other operators positions it'the capacity of the branch exchange is such as to require the services of more than one operator. Tn'such case, the resistance 57 shown in series with the busy signal 56 may be replaced by other busy signals. The lamp 53 serves as a calling signal on incoming calls over the trunk circuit. The other end of the trunk circuit T terminates in a nonnu- 108 and An answering or lis-- closure of a loop to connect a connector such as C with the trunk circuit @nly the line relays of the connector (l are shown, and the brushes of said connector are shown in corn nection with a called station E of the automatic exchange. The line finder N s shown muitipled to contacts in a be Oi (flier connector switch I and only so mach ct said has been brown as to connector r illustrate how the trunk circuit T ogerates on -ncoming calls from the automatic exchange. A complete disclosure of the au tomatic system is notdeemed necessary since it may be of any well-known type such as for example, that shown in Patent 1,281,013 of June 26th, 1917, to C. L. Goodrum.

deferring to Fig. 8 of the drawings there is shown a calling substation E at the man ual private branch exchange, apparatus of trunk circuit T which is located at the private branch excha. re and a cord circuit D which be used in interconnecting snip scribers lines such as E at the manual private branch exchange or in interconnecti subscribers of the manual exchange wi' the trunk circuit T The cord. circuit D is provided with the usual supervisory relays 105 and 123 and the supervisory lamps 107 and 126% for the purpose of providing supervision for the operator in interconnecting lines of the private branch exchange. In interconnectinga subscriber of the private branch exchange with the central oflice over the trunk ircuit T lamp 10? serves a supervisory signal and lamp 124-. as recall signal. .he core circuit D is provided with the usual ringing keys sing hey K is provided for the purpose of connecting the operators talking set, not shown, with the cord circuit. This key when actuated performs the additional function of associating the impulse sender S with the cord circuit when the cord circuit is utilized "for interconnecting a line terminating at the branch exchange with a trunk circuit T extending to the automatic exchange. The impulse sender S a set of relays whose function will hereafter be explained. a re peating coil R and condensers 115 and 116 are common to the operators position. it the operator fails to restore the key u ter having completed the impulse sending cp eration, an inductive path for conversational purposes for the calling and called subscriber is provided through the repeating coil R and the condensers 115 and 116.

The trunk circuit is of the two-way type and terminates in a jack 127 at the openators position. This trunk circuit may terminate in a line finder switch at an automatic exchange in a manner similar to that gization of trunk signal 129.

shown for the trunkcircuit T in F ig. 2 of the drawings. On incoming calls over the trunk circuit T ringing current responsive relay 130 is energized, thereby causing ener- Vilhen the operator answers by inserting a plug such as 126 into jack 127, the ringing current responsive relay 130 is disconnected from the jack, thereby extinguishing the trunk signal 129.

Referring to Figs. 1 and 2 of the drawlugs and assuming that the subscriber of station A has removed the receiver from its switchhook for the purpose of calling a subscriber at station B, at the automatic ex change, line relay 1 will be energized over a path extending from ground, upper normal contacts of jack 3, through the substation loop, lower normal contacts of jack 3, and through the winding of relay 1 to grounded battery. Line relay 1 is thereupon energized and at its armature and front contact. completesa circuit for line signal 2.

The operator noting signal 2,'insert s'plug 4 of the cord circuit into jack 3 of the calling line. Insertion of plug 4 into jack 3 disconnects line relay 1 from the calling line,

resulting in the extinguishment of line signal 2 and the energization of supervisory relay 6 associated with the answering end of the cord circuit 0. Supervisory lamp 7 of cord circuit 0 is prevented from lighting through the energization of relay 6 in the well-known manner.

The operator may then actuate the talking and dialing key K for the purpose of inquiring the wants of the calling subscriber. Having ascertained that station B at the automatic exchange is desired, the operator will then select an idle trunk circuit, such as T, which terminates in a jack 24 at her position and extends to the automatic exchange. Insertion of plug 23 into jack 24, completes a circuit for relay 66 over a path extending from grounded battery. winding of relay 66. tips of jack 24 and plug 23, upper normal contacts of relay 22, upper normal contacts of ringing key 14, upper right-hand winding of the repeating coil to ground, and a circuit for relay 51, over a pathextending from ground, lefthand normal contacts of relay 52, winding of relay 51. rings of jack 24 and plug 23, lower normal contacts of relay 22, lower normal contacts of ringing key 14, winding of supervisory relay 12, and lower righthand winding of repeating coil 5 to grounded battery. Relay 51 thereu ontperates and completes a circuit for relay 5( over a path extending from ground, upper right hand winding of. repeating coil 5, upper normal contacts of ringing key 14. upper normal contacts of relay 22, tips of plug 23 and jack 24, winding of relay armature and front contact of relay 5'1, inner right-hand normal contacts of relay 55, rings of jack 24 and plug 23, lower normal contacts of relay 22 and key 14, winding of supervisory relay 12,- and lower right-hand winding of repeating coil 5 to grounded battery. Relay 50 in operating completes a circu'it for slow-to-operate relay 58, over a path extending from grounded, battery, front contact and armature of relay 50, winding of relay 58',v and front contact and inner armature of relay 66 to ground. Relay 58 in operating completes a circuit for relay 54 over a path extending from ground, front contact and outer armature of relay 58, rightand lefthand windings of relay 54 in series, sleeves of jack 24 and plug 23, resistance 26, and thence in parallel, one path extending through resistance and armature and front contact of supervisory relay 12 to grounded battery and the other path through lamp 27 to grounded battery.

Lamp 27 is thus shunted and prevented from lighting. Relay 58 in operating also completes a circuit for relay 59 over a path extending from grounded battery, winding of relay 59, inner armature and front contact of relay 58 and front contact and inner armature of relay 66 to ground. Relay 59 in operating renders the talking conductors of the trunk T continuous. Relay 54 in operating locks up through its inner armature to ground. Relay 54 in operating also completes a circuit through its outer arina ture and front contact for relay 55. The busy signal 56 is energized when relay 52 releases by a circuit including the front contact and outer left-hand armature of relay 55, and armature and front contact of rela? 50."

In case the tip and ring of jack 24 is short circuited by the tip of the plug 23 of the cord circuit when plug is being inserted into jack 24 of the trunk current T. relays 51 and 66 will operate in series over a path extending from grounded battery. winding of relay 66., tip and ring of jack 24. (which have been assumed to be shortcircuited by the tip of the plug 23) and, winding of relay 51 to ground. Relay 66 in operating connects ground to the wirding of relay 58. and relay 51. in operating bridges relay across the tip and ring conduct-ors of the inner section of the trunk over a path extending from tip conductor of the inner section of the trunk T, wind ing of relay 50, armature and front contact: of relay 51. back contact and inner righthand armature of relay to the ring conductor of the inner section of the trunk T. Belay 50 will not operate at this time how-- ever due to the short-circuit across the tip and ring of the 24 of the trunk circuit T. Therefore, relay 58 will operate and the bridge will not be closed across the outer section the trunk, since relay 50 controls the successive energization of relays 58, 54 and 55, the latter of which causes the bridge to be placed across the outer section of the trunk. It is thus seen that the outer section or the trunk is not bridged to cause the operation of e switches at the automatic exchange until the plug 23 is fully inserted in the jack 2 1.

soon as the plug 23 is inserted relays 66, 51, 50, 58, 5 1, 59 and so are operated as heretofore described, and

' 'cuit is in condition for sending impulses. Upon the initial movement of the impulse sender or dial S from normal posi tion, relay 15 is operated over a circuit eX- tending trom ground, contacts 10 of dial S and winding of relay 15 to grounded battery. Rel .y 15 in operating, completes a circuit at its front contact and lower, inner armature tor relay l8, and opens at its outer, lower armature and back contact, the circuit leading to the operators telephone set. Relay 18 in operating completes a circuit for relay over apath extending from grounded battery. winding of relay 22, contacts 42 of key K, front contact and upper armature of relay 18 to ground. Relay 22 is thereupon energized and locks up over a path extending from grounded battery, winding of clay 22, contacts 42 of key K and outer, lower armature and front contacts of relay 22 to ground. Relay 22 in operating connects the impulse springs 41 of the dial S to the tip and ring conductors of the calling end or the cord circuit 0 and disconnects the answering end trom the calling end. Each time the dial S returns to normal position, relays 15 and 18 are deenergized. In returning to normal position, the contact 41 oi' the dial S will be opened a number of times corresponding to the digit dialed. In response to the impulses transmitted from the dial S, impulse relay 66 of the trunk circuit T will be intermit-' tently energized deenergized over a path extenning from grounded battery, winding of relay tips out jack 2a and plug 23, upper alternate contacts of relay 22, lower alternate contacts of relay 18, resistance 19, contact d1 of dial S, inner, lower alternate contacts of relay 22, jack 23 and plug 24 and winding ot rol 51 to ground. At the first release ot relay 66, in response to the first impulse transmitted thereto, relays 58 and release. function of relay 59 in releasing duri o the transmission of impulses is to short-circuit the retardation coil 1, resistance coil 60, and relay as well to .pen the incoming end of the trunk circuit. Relay 52 is preferably of the slowto operate type in order to prevent flashing of the supervisory lamp in case of a momentary operation of relay 65 during the transmission of impulses. Relay 58 is pref erably slow-to-operate inorder to prevent operation of relay 59 during the transmission of impulses. Relay 6a is of the slowto-release type and remains operated during the impulse sending period.

In accordance with each impulse transmitted from the dial S, impulses are repeated to an impulse relay such as 79 associated with an automatic switch at the automatic exchange over a path extending from grou 'id, left-hand winding of relay 79, brush 1, terminal 68, conductor 99, outer-right'- hand armature and front contact of relay 55, outer armature and front contact of relay G6, upoer norm l contacts of relay 59, conduc or 9S, terminal 70, and right-hand winding of relay 79 to grounded battery. After having sent a sufficient number of impulses to set the connector switch upon the ter ininals or" the desired station E, the operator may restore the key K to normal position.-

Station B may then be signaled in the wellknown manner. ld hen the called subscriber responds, talking battery will be supplied to his station from a relay 85. The calling subscriber A will be supplied with talking battery through the winnings of repeating coil 5 of the cord circuit G. If the operator fails to restore the key l: to normal after dial ig, a talking circuit, independent of the normal talking conductors of the cord circuit O and common to the cord circuits of the operators position, is available, said talking circuit including the upper and intermediate contacts of relay 22, condensers l6 and 17, outer and inner upper contacts of relay 15 and upper and intermediate contacts of key K. The operators telephone circuit (not shown) is bridged across this circu t and when conversation over the trunk circuit commences, the operator will be able to hear either party talking so that she is thereby audibly informed that she has failed to restore the key K to normal position. The operator, hearing conversation, will immediately restore the key K to normal. After the completion of conversation, and restoration of the receiver to the switchhook at substation A, supervisory relay 6 of the cord circuit C will be deenergized, thereby causing the lighting of supervisory lamp 7, in the well-known manner, which serves as an indication to the operator that conversation is completed. The operator may thereupon remove the plugs 1 and 23 from their associated jacks. Removal 0t plug 23 from jack 24 will cause the restoration of th release of the cord circuit O to normal position, thereby resulting in the interruption of the loop across the outgoing end of the trunk circuit which will cause release of the switches at the automatic exchange in the well-known manner.

On incoming calls over the trunk circuit T to the operators position, the ringing cur rent responsive relay 65 may be energized due to the application of ringing current to the conductors 98 and 99, extending from the automatic exchange to the manual exchange. The path for the energization of relay 6; may traced as follows: ground, side switch arm 93 in its third position, brush 67, terminal 90, conductor 98, winding of relay of), normal contacts of relay 64, condenser 63, conductor 9?). terminal 91, brush 89, side switch arm 9% in its third position, winding of relay 95, armature and front contact of relay 96, (relay 96 being operated), to a source of ringing current 97. Relay in operating completes a. circuit at its armature and front contact for slowto opcrate relay 52. Relay 52 in operating i up through its right-hand contact and 1 01.55.61 left-hand normal contacts of relay and completes circuit for line signal and busy signal 56 over a path extendi I urn and front contact of relay 52 and "100 in parallel, one path extending of relay and line lamp 53 to ground and other through busy signal 56 and re- .nstance to ground. In place of resistance 5. a number of busy signals may appear in es with busy signal 56 at other operators position. thus indicating to such other opmators that the trunk circuit. terminating in cl: 2% which is multipled to other po sitions. is busy. Trunk signal 53 serves my Relay 55 in operating, rcuit for trunk signal 53, there- The busy sig- "ized however relay retracts its armature due to a ri -cult tht'irefor being maintained through inner. left-hand contact of relay 55. Ime repeating relay 66 men 0 ierates over a circuit previously traced and in energizcompletes a circuit through it inner "ire and front contact for relays and .l through its outer armature and front t places a :fldge across the outgoing "he trunk circuit to trip the mac I g. The bridged circuit may be tracer from tip conductor 98 trunk the upper normal contacts of A an natiufe lease opens 1 by extin uishing said s gnal.

nal is maintained ringing at the autoi t er-change is tripped, the side swi ch are moved in the fourth position, "E34 ow -l ni flu: l i H10 Pt; acres p awng W .uiscri e1 at the ad. 0

maticexchange in conversational relationaship with the operator at the manual exchange. Itelay 58 in operating completes a circuit for relay 59 over a path eXtendin from grounded battery, winding of relay 59, inner left-hand armature and front contact of rela 58 and front contact and inner armature of relay 66 to ground. Relay 58 in operating also removes the short circuit from relay 51. Relay 6?: in operating places relay and condenser 62 in parallel with coil 61 and resistance 60 as herebefore described. When relay 59 operates, it renders the tip and ring talking conductors of the trunk circuit continuous and removes the shunt from the retardation coil 61 and resistance 60. Current now flows from relay 200 of the connector switch over a path extending from ground, left-hand winding of relay 200, side switch arm 93 in its fourth position, brush 87, terminal 90, conductor 98, through resistance 60 and retardation coil 61, front contact and outer armature of relay 66 front contact and outer right-hand ari'nature of relay 55, conductor '99, terminal 91, brush 89, side switch'arm 94 in its fourth position and right-hand winding of relay 200 to grounded battery.

The operator maythen actuate the talking and dialing key K for the purpose of inquiring the wants of the calling subscriber and assuming that substation A. is desired, may insert the plug 1 into jack 3 and then actuate ringing key 10 to signal the desired subscriber in the well known manner. When the subscriber at the substation A responds, supervisory lamp 7 will be extinguished.

Upon completion of conversation, supervisory lamp 7 will glow, thus indicating to the operator that conversation has ceased. The operator may then remove plugs 4 and 23 from their associated jacks whereupon all apparatus will be restored to normal and the system is ready for the next call.

Referring to Fig. 3 of the drawings, it will be assumed that the subscriber of station E desires connection with a trunk circuit T leading to an automatic exchange. Upon removal of the receiver from the switchhook at station E, a circuit is established for line relay 100 over path extend ing from grounded battery winding of relay 100, lower normal contacts of jack 102 through the substation loop and upper normal'contacts of jack 102 to ground. Relay 100 is thereupon energized and completes a circuit through its armature and front contact for line lamp 101, which causes said lamp to glow and to serve as a calling sig nal for the calling station E.

The operator noting the signal. inserts plug 103 of the cord circuit D into jack 102, thereby causing the deenergization of line relay 100, which, in retracting its armature,

ill

opens the circuit for line lamp 101. Insertion of plug 103 into jack 102 also completes a circuit for supervisory relay 105 of the cord circuit D, thereby preventing supervisory lamp 107 of the cord circuit D from lighting. Supervisory relay 105 is energized over path extending from ground, back contact and upper outer armature of relay 121, upper winding of retardation coil 112, upper normal contacts of relay 109, upper normal contacts of ringing key 108, tips of plug 103 and jack 102 through the substation loop, rings of jack 102 and plug 103, lower normal contacts of ringing key 108, through the winding of supervisory relay 105 and the upper and lower windings of resistance 10a in parallel to the lower normal contacts of relay 109, lower winding of retardation coil 112, back contact and upper inner armature of relay 121 to grounded battery.

The operator may then actuate the talking and dialing key K thereby placing the operators telephone set (not shown) in operative relationship with the calling station. The operators telephone set is connected with the tip and ring conductors 198 and 199, respectively of the cord circuit over a path extending from conductor 6 outer normal contacts of relay 119, contacts 152 of key K to the tip conductor 198 of the cord circuit and from conductor N, through the outer right-hand armature and back contact of relay 113, inner normal contacts of relay 119, contact 156 of key K to the ring conductor 199 of the cord circuit. After inquiring the wants of the calling subscriber and assuming that a connection with a subscriber of the automatic exchange is desired, the operator may insert plug 126 of the cord circuit D into the jack 127 of an idle trunk such as T extending to the automatic exchange. Insertion of plug 126 into jack 127 causes the operation of relay 121 over path extending from ground, winding of relay 121, sleeves of plug 126 and jack 127 and resistance 128 to grounded battery. Relay 121 is thereupon energized. In attracting its armatures, relay 121 bridges retardation coil 112 across the cord circuit D over a path extending from tip conductor 198 of the cord circuit through the upper winding of retardation coil 112, upper outer armature and front contact of relay 121, back contact of inner lefthand armature of relay 106, and lower winding of retardation coil 112, to the ring conductor 199 of the cord circuit. Relay 121 in attracting its armatures also completes a circuit for relay 106 over a path extending from grounded battery, upper inner armature and front contact of relay 121, winding of relay 106, front contact and armature of relay 105, sleeves of plug 103 and ack 102 to ground. Relay 106 in energizing, locks up through its front contact and inner right-hand armature and through contacts 153 of key K to ground at the operators telephone set over conductor .-7L as soon as key K is restored to no al position. Relay 106 in attracting its inner left-hand armature, opens the bridge of the retardation coil 112, but the switches at these atic exchange are operated and held by the retardation coil 120 which is b' across the trunk circuit when the key 11 is operated or by the subscribers loop.

The operator may then proceed to actuate the impulse sender or dial S to send impulses over the trunk circuit T to the automatic exchange for the purpose of operating switches thereat. Upon the initial actuation of the dial, relay 113 is operated over path extending from ground through off normal contacts 155 of the dial S and winding of relay 113 to grounded battery. Relay 113 is thereupon energized and at its right-hand contacts disconnects ring conductor N, extending to the operators telephone set from the cord circuit and at its left-hand contacts completes a circuit for relay 11%. Relay 11% thereupon energizes and at its right-hand contacts disconnects retardation coil 120 from the calling end of the cord circuit and bridges the interrupting contacts 154: of the dial S across the tip and ring conductors 196 and 197, respectively of the cord circuit over path extending from conductor 197 through contacts 151 of key K right-hand alternate contacts of relay 114, contacts 154 of dial S contacts 150 of key K to tip conductor 196 of the cord circuit. Relay 114 in operating also completes a circuit at its left-hand armature and front contact for relay 119, which in operating disconnects battery and ground at the automatic exchange from the calling substation and connects battery and ground thereto over a path extending from ground, upper winding of relay 118, upper right-hand winding of repeating coil R, left-hand alternate contacts of relay 119, contacts 152 of key K tip conductor 198 of the cord circuit D, upper normal contacts of relay 109, upper normal contacts of ringing key 108, tips of plug 103 and jack 102 through the substation loop, rings of jack 102 and plug 103, lower normal contacts of ringing key 108 through the winding of relay .105 and the upper winding of resistance 104 in parallel to the lower normal contacts of relay 109, contacts 156 of key K inner alternate contacts of relay 119, lower right-hand winding of repeating coil R and lower winding of relay 118 to grounded battery. Supervisory relay 105 of the answering end of the cord circuit is thus maintained energized when the battery from the central cities is disconnected from the calling substation. Relay 118 is operated over the path traced and completes position relays 113 and 11 1 release.

7 manner.

After the dialing operation is completed, the operator may restore key K to normal position, thereby establishing a talking circuit for the calling subscriber to the trunk (onductors 160 and 161 of the trunk circuit T over a path extending from conductor 160, tips of jack 127 and plug 126, upper normal contacts of ringing key 125, "-conductor 196, contacts 158 of key K conductor 198, upper normal contacts of relay 125, lin s of plug 126 and jack 127 to trunk conductor 161. Restoration of key K to normal position completes a locking circuit of relay 106 heretofore traced, and causes the release of relays 1'18 and 119, so that the dial be associated with another cord circuit at the. operators position.

If the operator fails to restore the key K to normal after dialing, a talking path, independent of the normally continuous talking conductors, will be provided through the repeating coil R which is common to the position, said path including contacts 150, 152, 156 and 151 of key K right and left hand windings of repeating coil R, condensers 115 and 116, winding of relay 118 and alternate contacts of relay 119. The operators telephone set is, at this time, connected across this circuit and the operator may thus be audibly informed, when conversation commences, that she has failed to restore the key to normal. The operator, hearing the conversation, may then restore key K to normal position.

Upon completion of conversation and restoration of the receiver to the switchhook at substation E, supervisory relay 105 will be deprived of current thereby causing the release of this relay and the lighting of supervisory signal 107, which serves as a disconnect signal to the operator. Relay 105 in releasing also completes a circuit for'splitting relay 109 over a path extending from ground, sleeves of jack 102 and plug 103,,

armature and back contact of relay 105, front contact and outer right-hand armature of relay 106, and winding of relay 109 to grounded battery. Relay 109 thereupon attracts its armatures thereby disconnecting the answering plug 103 from the calling plug 126 and connecting ground and battery to the tip and ring conductors, respectively of the answering end of the cord circuit.

The operator noting the disconnect signal 107 may remove the plugs 103 and 126 from' their associated jacks, whereupon the line and trunk circuits are ready for the next call. a

It will now be assumed that a call has arrived at the operators position over trunk circuit T due to a source of ringing current being applied to the trunk conductors 160 and 161. Applying ringing current to the trunk conductors 160 and 161 causes the energization of 130 over a path extending from conductor 160 upper normal contacts of jack 127, right-hand winding of relay 130, condenser 131 to conductor 161. Relay 130 in operating completes a locking circuit for itself and a circuit for the lighting of lamp 129 over a path extending from ground, armature and front contact of relay 130, through the lower normal contacts of jack 127 and thence in parallel, one path extending through lamp 129 to grounded battery and the other through the left-hand winding of relay 180 to grounded battery. The operator noting the trunk signal 129 inserts plug 126 into jack 127, whereupon the locking'circuit for relay 130 is opened thereby causing the deenergiZat-ion of said relay and the consequent extinguishment of trunk signal 129. Insertion of plug 126 into jack 127 alsocompletes a circuit for relay 121 over a path extending from ground, winding of relay 121, sleeves of plug 126 and jack 127 and resistance 128 to grounded battery. Relay 121 in operating bridges retardation coil 112 across the cord circuit over a path extending from conductor 198 of the cord circuit, upper winding of retardation coil 112, upper outer armature and front contact of relay 121, back contact and inner left-hand armature of relay 106 and lower winding of retardation coil 112 to conductor 199 of the cord circuit. thereby tripping ringing at the automatic exchange, if the call is from an automatic ringing source.

The operator may then actuate the key K to inquire the wants of the calling subscriber and after having ascertained the station desired restores key K to normal. Assuming that station E is desired, the operator inserts plug 103 into the jack 102 and then actuates ringing key 108 to signal the station E in the well-known manner. Insertion of plug 103 in the jack 102 cornpletes a circuit for supervisory lamp 107 over a path extending from grounded battery, through lamp 107, back contact and armature of relay 105, sleeves of plug 103 and i 1 102 to ground. hen the calling subscrioer responds, supervisory relay 105 operates due to current flowing from the connector switch at the automatic'exchange he trunk and cord circuit and the subsciroers loop in parallel with the path through retardation coil 112. Supervisory lamp 107 is tnereupon extinguished indicating to the operator that the called subscriber has responded. Relay 105 in operating also completes a circuit for relay 106 over a path intending from ground, sleeves of jack 102 and plug 103, armature and front contact of relay 105, winding of relay 106, front contact of upper inner armature of relay 121 to grounded battery. Relay 106 in operating locks up through its front contact and inner right-hand armature and contacts 153 of key K to ground at the operators telephone set. Relay 106 in operating also opens the circuit, at its back contact and inner left-hand armature, of the retardation coil bridge, and reduces the resistance of the shunt around the Winding of supervisory relay 105 by short-circuiting the lower winding of resistance 10% by the closure of its outer left-hand armature and front contact. Due to the energization of relay 106, the retardation coil bridge, as before stated, is removed from the line thereby placing the connection under the control of station E.

Upon completion of conversation and restorat on of the receiver to the switchhook at station E, relay 105 releases'due to the opening of the directcurrent path at the substation, thereby closing a circuit for supervisory lamp 107. A circuit is also closed for sglitting relay 109 over a path extending from grounded battery, winding of relay 109, outer right-hand armature and front contact of relay 106, back contact and armature of relay 105, sleeves of plug 103 and jack 102 to ground. Relay 109 in operating disconnects the calling from the called end of the cord circuit and connects battery and ground through its lower and upper alternate contacts, respectively, to the answering end of the cord circuit. If the operator does not immediately take down the connection and the subscriber of station E, desires to make another call, the operator may be signalled-by means of the super- *isory lamp 107. If, before the operator takes down the connection, a call arrives over the trunk circuit T thecalling station E will not be signalled, but the ringing current will pass through ringing current responsive relay 110 and condenser 111 thereby energizing relay 110 and completing a circuit for lamp 12 over a path extending from grounded battery, through lamp 124 an front contact and armature of relay 110 to ground. Lamp 1% will be lighted time relay 110 is energized and serves as a recall signal for the operator. The operator noting the recall signal may actuate tl e key K and inquire the wants of the calling subscriber and then complete the connection as heretofore described.

llhat is claimed is:

1. in a telephone system, a cord circuit having normally continuous talkingv conductors terminating in an answering and a calling plug, an operators key, an impulse sender, means responsive to the actuation of the key and the'sender for rendering the talking conductors of the cord circuit discontinuous, and a talking path provided ditl'ering from the normally continuous talking conductors of the cord circuit if the opera-tons key is not restored to normal.

2. In a telephone system, a cord circuit having normally continuous talking conductors terminating in an answering and a calling plug, an operators key, an impulse sender having a forward and backward movement, means responsive to the actua tion of the operators key for associating the sender with the cord circuit, means responsive to the forward movement of the sender for rendering the talking conductors of the cord circuit discontinuous, a trunk circuit connected to the calling terminal of the cord circuit terminating in an automatic switch, means responsive to the backward movement of the sender for settingthe switch and a talking path provided differing from the normally continuous talking conductors of the cord circuit if the key is not restored to normal.

3. In a telephone system, a cord circuit having normally continuous talking conductors terminating in an answering and a calling plug, an operators telephone circuit, an impulse sender having a forward and backward movement, a trunk circuit connected to the calling plug ot the cord circuit and terminating in an automatic switch, an operators key adapted upon actuation to connect the operators telephone set to the cord circuit and to associate the impulse sender with the cord circuit, means responsive to the forward movement of the impulse sender for disconnecting the operators telephone .set from the cord circuit and for rendering the talking conductors of the cord circuit discontinuous, means responsive tothe backward movement of the impulse sender for controlling the operation of the automatic switch, and means for providing atalking path through the cord circuit if the operators key is not restored to normal.

4:. In a telephone system, a cord circuit having normally continuous talking conductors, an operators key, an impulse sender, means responsive to the actuation of the key and sender for rendering the talking conductors discontinuous, and a talking path provided differing from the normally continuous talking conductors if the operators key is not restored to normal.

5. In a telephone system, a cord circuit terminating in a pair of plugs, a talking circuit normally connecting said plugs, an operators key, an impulse sender, means responsive to the successive actuation of said key and said sender for interrupting aid talking circuit, and a talking circuit which is different from said normal talking circuit it said key is not restored to normal.

6. In a telephone exchange system, a plurality of cord circuits each having normally continuous talking conductors, a key for each cord circuit, an impulse sender common to said cord circuits, means responsive to the actuation of the key of a cord circuit for associating the sender therewith, means responsive to the actuation of the sender for rendering the talking conductors of the cord circuit discontinuous, and a talking path differing from the normal talking circuit if the operators key is not restored to normal.

7. In a telephone system, an operators position, a plurality of cord circuits thereat, an operators key for each cord circuit, an impulse sender common to said cord circuits,

- means responsive to the actuation of a key for associating said sender with a cord circuit, means responsive to the actuation of the sender for disconnecting the answering from the calling end of the cord circuit, and inductive talking path for uniting the answering and calling ends of the cord circuit immediately after said sender has been actuated.

8. In a telephone system, an operators position, subscribers lines and trunk lines terminating thereat, cord circuits at said po sition each having a key associated therewith, an impulse sender for said position, and circuit connections controlled by a key of one of said cord circuits and said impulse sender, whereby in extending a call from a subscribers line over said trunk circuit, a talking path is provided if the operator fails to restore the key after having operated the impulse sender.

9. In a telephone system, an operators position, subscribers linesand trunk lines terminating therein, a plurality of cord circuits for interconnecting said subscribers lines and trunk lines, an operators telephone circuit at said position, a key for each cord circuit for connecting said operators telephone set to said cord circuit when answering a call, an impulse sender for said position, means including said sender for establishing a. talking connection over one ofsaid cord circuits and one of said trunk lines between two subscribers lines, andmeans whereby said talking connection isrmaintained between said lines it the operator fails to restore'the said key.

105 In a telephonesystem', atwo-way two conductor trunk circuit terminating; at one end in a jack at an operators position and at the other end in an automatic switch, a cord circuit terminating in a plug for extending a call over said trunk circuit, a relay connected to said trunk circuit energized upon the insertion of the plug of the cord circuit into the jack of the trunk circuit, a second relay cooperating with said first mentioned relay for closing a bridge across said trunk circuit to operate said auto matic switch, and means for preventing the energization of said second relay until the plug of the cord circuit has been completely inserted into the jack.

11. In a telephone system, a trunk circuit having inner and outer sections, said inner section terminating in a jack and said outer section terminating in an automatic switch, a repeating relay connected to the inner section of said trunk circuit, a second relay cooperating with said repeating relay upon energization for bridging the outer section of said trunk circuit, a cord circuit terminating in an answering and a calling plug, a circuit completed for said repeating relay when the calling plug of said cord circuit is inserted into the jack of said trunk circuit, and a third relay associated with said trunk circuit for delaying the operation of said second relay until the plug of said cord circuit is completely inserted into the jack of said trunk circuit.

12. In a telephone system, a private branch exchange, extensions leading therefrom, a trunk line extending from said exchange to a main central office, a cord circuit for establishing connections between said extensions and said trunk line, an operators set including dialing means for controlling the operation of mechanical switches for association with said cord circuit, means where by, when said operators set is associated with the cord circuit and said dialing means is operated to control mechanical switches at the main central office, the end of the cord circuit associated with an extension will be disconnected from the end associated with the trunk line, and means whereby at the completion of the dialing operation, the two ends of the cord circuit may be interconnected for talking purposes through the operator s set.

13. In a telephone system, a private branch exchange, extensions leading therefrom, a

lib)

trunk line extending from said exchange to the main central oflice, a cord circuit for establishing connections between said extensions and said trunk line, an operators set including dialing means for controlling mechanical switches associated With said cord circuit, means automatically responding to the operation of said dialing means to disconnect the end of the cord circuit asso- 1 ciated With the extension from the end associated with said trunk line, and means automatically functioning, at the end of the dialing operation, to interconnect the two ends of the cord circuit through the operators set for talking purposes.

In Witness whereof, I hereunto subscribe my name this 18th day of October, A. D. 1920.

WALTER B. STRICKLER. 

